The present invention relates generally to pneumatic devices and, in certain embodiments, to air motors with valves having magnetic detents.
Pneumatic motors are often used to convert energy stored in the form of compressed air into kinetic energy. For instance, compressed air may be used to drive a reciprocating rod or rotating shaft. The resulting motion may be used for a variety of applications, including, for example, pumping a liquid to a spray gun. In some spray gun applications, the pneumatic motor may drive a pump, and the pump may convey a coating liquid, such as paint.
Conventional pneumatic motors are inadequate in some regards. For example, the mechanical motion produced by the pneumatic motor may not be smooth. Switching devices in pneumatic motors may signal when to re-route pressurized air during a cycle of the motor. When operating, the switching devices may intermittently consume a portion of the kinetic energy that the pneumatic motor would otherwise output. As a result, the output motion or power may vary, and the flow rate of a liquid being pumped may fluctuate. Variations in flow rate may be particularly problematic when pumping a coating liquid to a spray gun. The spray pattern may contract when the flow rate drops and expand when the flow rate rises, which may result in an uneven application of the coating liquid.
The switching devices in conventional pneumatic motors can produce other problems as well. For example, some types of switching devices, such as reed valves, may quickly wear out or be damaged by vibrations from the pneumatic motor, thereby potentially increasing maintenance costs. Further, some types of switching devices may be unresponsive at low pressures, e.g., less than 25 psi. Unresponsive switching devices may impede use of the pneumatic motor in applications where low-speed motion is desired or higher pressure air supplies are not available.